<!DOCTYPE HTML>
<html>

<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <title>if...else</title>
  <script type="text/JavaScript">
    var myage =99;//赵红的年龄为99
if(myage<=44)
  {document.write("青年");}
else if(myage<=59) 
  {document.write("中年人");}
else if (myage<=89)
  {document.write("老年人");}
else
  {document.write("长寿老年人");}
</script>
</head>

<body>
</body>

</html>